Re: Bad quality of autohinting with arial at 15 points.

[Antoine Leca]

Ramón García Fernández wrote:
> 
> With arial.ttf and times.ttf (from www.microsoft.com/typography) at 15 ppem,
> the autohinter shows a quite boldened font, compared to the native truetype
> hinted font, or the unhinted font.

I am surprised it shows light with the unhinted. Arial stems are about 160-180
FUnits wide, so they should appear 1-pixel wide when unhinted at 15ppem (or
even 17 ppem, so below for;more), that's correct.
About Times, the width are 192 FUnits for the straight stems (so you're right
at 15 ppem, but it changes at 16!) and around 225 for the rounded (like D, O),
so they should appear 2-pixel wide (a little fatty) at 15 ppem. Right?
Furthermore, ronding errors will lead to have 2-pixel wide stems anyway
(like Times M, left part).

Regarding the hinted version, I believe this is an artefact of the design.
For not bold font, MS do use hinting to prevent the stems to go 2-pixel wide
until 17 ppem (which are 12 pt @ 96 dpi), because normal users expect
such a point size to appear 1-pixel wide, unless the font is in bold version.
So the hints (the TT program) specifically modify the stem width to assure
that (and in fact, this is a big part of what they do, along with the
perservation of the general design).

More on this:
<URL:http://www.microsoft.com/typography/developers/delivery/hinting.htm>
<URL:http://www.microsoft.com/typography/developers/delivery/deliver.htm>

Worth reading for the auto-hinting developpers, I believe!

 
Antoine